Regulated alternator



Oct. 3, 1961 F. BENJAMIN :rAL

REGULATBD ALTmNATQR 2 Shoots-Shut FilOd llay 2, 1958 FIG.I

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.1 3,003,101 I I II GULATED ALTERNATOR ma Benjamin, L: Minds, and Arthur nssnoenren v come-la, on to American Electronics This invention relatesto regulators, and more particu larly to a voltage regulating system for an alternating current generator 'or:alternator, and particularly a multipurpose of regulating the line voltage with variation in 1,

load. Such regulators often take the form of adjustable irnpedances or resistances placed either in series. ineach ice;

by sensing theToutput voltage and varying the in such a way as to continuously maintain the output voltage as stable as possible." '1 t As noted hereinbefore, line regulation corrects not only for imbalance among phases, but also corrects tor the over-all voltage drop which occurs when the system is loaded. However, it introduces severe harmonic distortion, and in. addition is. quite costly because of the large size of the;reactrs or impedances which must be employed to compensate for the wide variationin line voltagewithwidevariation in loading. h 1 Where vthe expense of line regulation is not justified, it

been customary to employ field regulation. In these of the phases of thelline, or in shunt between phas'es or between each phase andthe-neutral. Such line regulators serve to maintain line voltages substantially at the proper 1;

level and also tend to" eliminate imbalance in and among line voltages due to imbalance in load on the three phases. They have the serious disadvantage, however,

that they 'inherentlyintroduce sever harmonic distortion;

' and his an object of this invention to provide alternator Q:

voltage regulation which does not introduce severe 'or even objectionable harmonic distortion into the line.

Where severe variations" in load on the three phaseline must beanticipated-it has been necessary to make the line regulators, i.e., the three adjustable impedances, of

suflicient size and magnitude to accommodate the maximum span between light loading and heavy loading. It

' is accordingly another object ofthis invention to provide a: voltage regulating system having appreciably smaller 1 weight and bulk and consequent smaller costthanprevi- 3: ous systems. It is another object to provide a voltage regulation system which 1willjincrease alternator longevity. It is a further object to' provide a system having better regulation than heretofore. I

In a three-phase system having no regulatorgan'imbalance in load among the three phases produces an imbalance in line voltagesas well, as -an over-alludrop in average or mean line voltage. In the past it has been customary, where justified economically, to employ line regulation for notonly regulating the over-all or average voltage among the phases, but also to balance the three phases. One regulator per phase is required,- so that'in the case of ,a three-phase systmnihreesuch regulators would be required. .Several'differenttypesoflineregulators are known inthe'art, oneitype [of regulator,

as the ferto-resonanttypeforconstantvOltage trans former," is simple and economical, lbutiits'useiis'jrestrictcd to applications where only the input voltage varies. For satisfactory operation the inputjfrequeiicyfand the load on the output must be fixed. regulatorconsists generally oia partially saturating transformer across the output or secondary or wlfiehisfbo neted a capacitor. 3

continually adjust its value the Insrnular' a a 0 m a as su m r the phases otthe buaggenerally being connected average line voltage.

systems the output voltage or voltages are sensed, applied against a reference standard, and the difierence employed to control an-arnplifier which in turn feeds thealternator field. 'Field; regulation of this type serves to and compensate for loading on an average or over-all or gfor-one particular phase,' but'is unable to with @ph fi -ir ubalance,,.since-;all phases must be adjusted ihhuiillyli Thus, while .it corrects the aver age voltage. amongthe phases, or oneparticular haseQit'does .not help with phaseimbalance, therefore'some may? well over the rated voltage while others may be seriously-under the ratedvoltagel As noted .hcreinbefore', line regulation, except .forthe objectionable phase distortion, has been recognized as .beingsuitable for'correction of, both imbalance and, general. voltage fluctuation, although the ,cost has been high;becauseofgthe large p gregulatorsmquired. Field regulation has been turned to'inthose instances where the expense of the costly line regulation ,wasanot, justified. ,No thought has even given to combining the two typesof regulation, for two reasons. .First, it has been felt that field regulation is sirnply 'a less desirable but more economical form of regulation than line regulation and tha'tline regulation by..itself accomplishes essentially everything required; and, secondly, it has been tacitly assumed that types ot regulation would be implicitly incompatible, since the .line regulation implicity has a capacity for up the entire linevoltage, which is essentially the function of f the field regulatiomandit'has in the' past been tacitly iassurned thatany attemptto combine two of regulation would lead to instability, in thateach regulator .would. attempt to take over or control or However, in accordance with the present invention, both typesof regulation, line regulation and fieldregulation, are employed to regulate the alternator output: and

unexpected synergistic advantages have resulted. I,

In the firstplace, it has been found that by simultaneously applying both types ofregulation to the alternator and its output line, harn1'onic distortionhas been reduced almost to insignificanceQQ It has been furthertound that 'with the present invention the large bulky line regulators 1 which would normally have to be employedfor a given system, may he: measurably from [What would be required if field regulation werenot simultaneously used. The-net result is that although the field regulator must be slightly larger than would otherwise flbe thejcase without line regulation, the decrease in size I of the regulators is so much more marked that the total bulk, weight and cost of the entire regulation system wia ulrueh less than would be required with conventional :rregulation equipment to achieve the same extent of regulationrrln other words, it has been foundthat line and fielcljre'gulation are not linear functions and that there- -.toretheIcombination of the two produces far more than ithe expected sum of the two when used individually.

Specific schematic forms of the present invention are illustrated in the accompanying drawings, wherein:

FIG. 1 shows schematically a system constructed in accordance with the present invention;

FIG. 2 is a more detailed schematic .diagram of one of the components illustrated in FIG. 1;

FIG. 3 is a further detailed schematic diagram of certain other components shown in FIG. 1;

FIG. 4 illustrated an alternative construction of one of the elements or components shown in FIG. 3; and

FIG. 5 is a representative example of the nature of one of the other elements or components shown in FIG. 1.

FIG. 6 shows an alternative form of the component illustrated in FIG. 2. 7

Referring to the drawings, and particularly to FIG. 1, there is illustrated a regulated multi-phase electric system, particularly a three-phase system, having three output wires 11, '12 and 13, and a neutral or return wire 14, which together constitute a three-phase output bus 16. Feeding power to the bus 16 is a three-phase alternator 17, having, in the example shown, a Y-connected armature 18 and a field winding 19.

Field current is applied to the field winding 19'. by field current means shown schematically at 21 and consisting essentially of an amplifier 22, the output of which is ap plied to the field winding 19 as shown at 23. The output of the amplifier 22 is regulated in accordance with the difference between a reference voltage from a standard 24 and a sensed voltage from 25, which are combined at 26 and fed to the amplifier 22. The sensing mechanism 25 has voltages from the three phases 11, 12 and 13 fed to it by means of sensing leads or wires 27. If desired, sensing could be confined to a single phase, or alternatively could incorporate the neutral 31, as shown in FIG. 6.

The regulating system of the present invention also includes an adjustable impedance means 28 connected to the bus 16 and regulated by a regulating means 29 to and known form, such as is shown by way of example on page 419 of the book entitled Magnetic Amplifiers, by H. F. Storm, published by John Wiley & Sons.

For field regulation, the voltage between any one of the phases 11-13 and the neutral 14 may be applied to the sensing means 25 and used to control the current in the field winding 19, or an average or mean of all three phase voltages may be taken, as shown by the exemplary sensing means 25 in FIG. 2. In FIG. 2 the leads from the three phases 27 are applied to the matrix of rectifiers 32 and an average'is then applied to thevoutput leads 33, feeding to the comparator 26. This average is then compared in 26 with the standard stable reference voltage 24, and the difierence is employed to drive the amplifier 22.

An alternative sensing means 25a is shown in FIG. 6 wherein the three phases 27 are half-wave rectified by the diode matrix 32a and combined to form the positive output. The neutral 31 passes through as the negative output. 7

The regulator 29 and impedance means 28 may take the form shown in FIG. 3 if desired. In this figure the respective voltages between each of the phases 27 and the neutral 31 are applied to a sensing means 34 and thence compared with a standard reference voltage from 36, the difference being applied to an amplifier 37, the output of which serves to adjust or regulate the magnitude of an adjustable impedance 38 connected in shunt across the associated phase, for example the phase 11, and the neutral 14. Under some conditions the amplifier 37 is unnecessary. This system is a typical shunt line regulator system and functions in manner well known.

Where series rather than shunt regulation is desired for the line the impedance means may take the form shown in FIG. 4, wherein impedances 39 are connected in series in each of the respective phases 11, 12 and 13, the magnitudes, as before, being controlled by the voltages of their respective leads or phases.

The amplifiers, for example the amplifier 22 shown in FIG. 1, may take the form of a magnetic amplifier (FIG. 5) having gate windings 41 and a control winding 42 fed from the leads 43. The amplifier is supplied with a source of power at 44 and the output applied to the leads 23 and thence to the field winding 19.

A system constructed in accordance with the present invention has been tested meticulously and found, to have marked advantages over systems previously known. The following table shows the results of a test of a system having line regulation only.

Load Current Base Voltage Test N0. P.F. Lag

A B qSC qSA B 450 N L NL NL 115 115 115 1. 0 FL FL FL 114. 7 114. 7 114. 8 0.8 FL FL FL 115 114.9 114. 8 0. .FL FL FL 112.3 112. 5 112. 1 1. 0 NL NL Fl 114.4 115. 8 114. 3 0. 8 NL NL FL 116 116. 5 114. 4 0. 75 NL NL FL 113. 3 114. 5 111.8 1.0 NL FL FL 114. 9 114. 9 113. 5 0. 8 NL FL FL 117 115. 2 114. 8 0. 75 NL FL FL 114 113 111. 5

Reactor Current L-N Total Distortion Test No.

A 4;]; 50 4.11 sB e0 The following table shows the result when field regulation as well as line regulation is employed, in accordance with the present invention.

Load Current Phase Voltage L-L Voltage 'l z est 1?.F. I

as B o A an 10 A1-2 112-1 113-1 1 NL NL NL 115 115 115 200. 8 200. 7 200. 6 2 1 0 FL FL FL 114.9 115. 114.9 200.5 200.0 199.8 3--..-- 0.8lag FL FL FL 114.8 114.6 114.9 199.5 200 200 4 1.0-- NL NL FL 113.6 116.4 114.8 201 204 196.8 5--.. 0.8 lag NL NL FL 115 116.3 113.9 202.2 202 197.8 6..... 0.8198(1... NL 'NL FL 112 115.7 115.? 198 205 196.2

NL FL FL 114.19 116 p 113 205 199.5 197 0. g lag..-" NL FL FL 116 114.7 112.6 201.2 197.0 198.8

Alt. Reactor Current Regulator Output L-N Distortion Tut No. 161%? 7 rent A B 50 M. e3 #10 5A 5B 410.

From the above the many advantages of the present means for applying field current to said field winding, inventionwill be noted. First it will be noted that the electric means for applying the voltage of at least one distortion, i.e., the harmonic distortion, has been markphase of the alternator output to said field current applyedly reduced. This is because the present invention ing means for controlling said field current in accordance draws much less current through the dummy load (i.e. with said phase voltage, adjustable impedance means com the impedances 38 in FIG. 3) than does the conventional nected to said output bus, and means responsive to the line regulation system without field regulation. output voltage of at least one phase of said alternator, for

Secondly, it will be noted that the size of the dummy controlling the value of said impedance means in accordload (saturable reactor, 38 in FIG. 3) may be greatly reance with said output voltage. duoed, because the size is determined principally by the 3. Regulated multi-phase electric system comprising: a largest current which it must pass. It will be seen from multi-phase alternator having a field winding, a multithe last table above cited, giving the results of the presphase output bus connected to the output of said alterent invention, that the largest current under any connator, means for applying field current to said field winddition, this being an 80 lagging power factor on the secing, means responsive to energy flow in at least one phase and and third phase, was 44 amps, whereas the largest of said output bus for regulating the field current applied current drawn with the standard'line regulator alone was to said field in accordance with said energy flow, adjust- 88 amps., this being underno load conditions, able impedance means connected across eachphase of Thirdly, the overall regulation is immeasurably better 30 said output bus, and regulating means connected to at because of the much smaller swing between maximum least one phase of said/output bus for regulating the and mnimum reactor current, i.e., current in the adjustmagnitude of said impedance means in accordance with able impedance 38 (FIG. 3). energy fiow in said last mentioned phase.

Finally, alternator life may be expected to be much 4. Regulated multi-phase electric system comprising: a improved with the present invention because the life exmulti-phase alternator having a field winding, a multipectancy of the field coils of an alternator varies inversely phase output bus connected to the output of said alterwith the field current time duration. In the firsttwo nator, means for applying field current to said field windtables the field current. remained constant at 18 amps, ing,.means responsive to energy flow in at least one phase whereas with the presentinvention it will be seen that the of said output bus for regulating the field current applied field current was varied from 13.5 to 19.6 amps. with the 40 to said field in accordance with said energy flow, adjustgeneral mean or average being appreciably less than the able reactor means interposed in each phase of said outconstant 18 amps. without the present invention. put bus and regulated means connected to at least one While the instant invention has been shown and dephase of said output bus for regulating the magnitude scribed herein in what is conceived to be the most pracof said reactor means in accordance wtih energy flow in' tics! and preferred embodiments, it is recognized that said last mentioned phase. departures may be made therefrom within the scope of 5. Regulated multi-phase electric system comprising: a theinvention which is therefore not to be limited to the multi-phase alternator having a field winding, a multidetails disclosed herein but is to be afforded the full scope phase output bus connected to the output of said alterof the claims. nator, means for applying field current to said field wind- What is claimed is: ing, means responsive to energy flow in at least one phase 1. Regulated multi-phase electric system comprising: a of said output bus for regulating the field current applied multi phase alternator having a field winding; a multito said field inaccordance with said energy flow, adjustphase output bus connected to the output of said alterable reactor means connected across each phase of said" nator; means for applying field current to said field output bus, and regulating means connected to at least winding; means responsive to energy flow in a least one one phase of said output bus for regulating the magniphase of said output bus for regulating the field current tude of said reactor means in accordance with energy. flow applied to said field in accordance with said energy flow; in said last mentioned'phase. v adjustable impedance means interposed in each phase of said output bus; and regulating means connected to at Refmices cued m the file of Patent. least one phase of said output bus for regulating the UNITED STATES PATENTS. magnitude of said impedance means in accordance with 903 5 0 Knapp'etl'aL 10 190 energy flow in said last mentioned phase. 1 125, 20 c li 1 126 19 1.5 2. Regulated three phase electric system comprising a 2,333,617 Smith N v; 2,, 1943 three phase alternator having a field winding, an output 2,758,272 Franklin .Aug. 7, 1956. bus connected to the output terminals of said alternator, 2,806,990 Evans Sept. 17, 1957, 

